Influence of water and terpenes on flammability in some dominant Mediterranean species

Abstract

Abstract. In the Mediterranean basin, fires are a major concern for forest and shrubland ecosystems. We studied flammability, its seasonality and its relationship with leaf moisture and volatile terpene content and emission in the dominant species of a Mediterranean shrubland and forest in Catalonia (NE Iberian Peninsula). We measured temperatures and time elapsed between the three flammability phases: smoke, pyrolysis and flame, for four seasons. We sampled twice in spring because of an occasional drought period during this season. Flammability had a significant relationship with leaf hydration, in the shrubland and in the forest. Few and only weak correlations were found between terpene content and flammability. In the future, arid conditions projected by climatic and ecophysiological models will increase fire risk through decreased hydration and subsequent increased flammability of the species.

Assessment of Flammability of Moroccan Forest Fuels: New Approach to Estimate the Flammability Index

“…Given that water use strategies control the quantity of water maintained inside plant cells under drought conditions in order to withstand drought, the two groups of plant species mentioned above may have distinct flammability behaviours, since the amount of heat required to evaporate water is positively correlated with MC [38]. Moreover, Alessio et al [35] and White and Zipperer [1] confirmed this fact by indicating that flammability was strictly related to MC due to physical and chemical mechanisms as well as physiological elements, especially whether the character is deciduous or evergreen as this can influence the plant flammability [1]. Indeed, the species examined in this paper are subdivided into drought-deciduous and evergreen sclerophyllous species.…”

“…Indeed, MC has a profound effect on different aspects of flammability [1,[35][36][37]49], especially TI [5,15,38] and flame characteristics [15,36]. Behm et al [39] considered MC as an indicator of ignitability inter alia.…”

“…Therefore, flammability variation within species depends on fuel water content [1,35,38]. Hence, there is the need for a flammability database as a function of MC within the same species [26], which can be expressed in practice through modelling functions of the relation flammability against MC.…”

“…Moisture content (MC) is a key factor influencing flammability (e.g., [5,17,35,36]), acting both physically on the plant by controlling the thermal capacity of tissues and chemically through the adjustment of the combustion process [1,37]. Therefore, flammability variation within species depends on fuel water content [1,35,38].…”

Calibration assessment of forest flammability potential in Italy

“…Notably, in Mediterranean trees (e.g., Pinaceae and Cupressaceae) the abundance of organic oils and organic volatile compounds and terpenes, whose flash points are low, largely contributes to the ignition and spread of fire (Alessio et al 2008); at the same time, the susceptibility to burn of any given fuel is manifested only under particular weather conditions, as it is largely dependent on fuel moisture content.…”